The most common and most likely answer to this crossword clue is the 5 letter word NARCO
I've seen this crossword clue in Financial Times
N
A
R
C
O
More clues leading to the result NARCO
- Drug dealer bowed, given new start
- I collar horse dealers west of Newbury — with bow
- Drug dealer participating in seminar complacently
- Drug runner is part of ring in New Orleans, initially
- Returning officer managed to find drug smuggler
- US drug dealer charged over company’s trimming
- Informant spoken to finally by man from drug squad
- Member of US drugs squad managed to turn over company
- A US cop charged over business
- US agent ran climbing business
Buddy explains!

The straight part
We know that "drug smuggler" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case drug smuggler = narco.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does NARCO mean?
NARCO noun- Narcotics.
- A South American drug baron.
- A police officer specializing in drug crimes
- Someone suffering from narcolepsy